Semiconductor device and method of manufacturing the same

ABSTRACT

A method of manufacturing a semiconductor device is disclosed. The method comprises: applying a sensing layer with variation in a secondary attribute according to heat, on a handle wafer; patterning the sensing layer, thus forming a cavity; forming a sensing part pattern having a beam structure in the cavity; forming a light-absorbing layer for converting energy of incident photons into heat, along the sensing part pattern; turning the entire structure over, removing the handle wafer, and thus exposing a rear portion of the sensing part pattern; and forming an additional light-absorbing layer on a rear portion of the light-absorbing layer formed on the sensing part pattern, thereby forming a sensing structure part having a beam structure. The method may further comprises: after the forming of the light-absorbing layer for converting the energy of the incident photons into the heat, forming on the light-absorbing layer a filling layer to fill up the cavity, and after the forming of the additional light-absorbing layer, selectively removing the filling layer and exposing the sensing structure part in a manner to float it over the cavity.

BACKGROUND

1. Field

The following description relates to a semiconductor device, and moreparticularly, to a micro-bolometer type infrared (IR) sensing device.

2. Description of the Related Art

A micro-bolometer type infrared (IR) sensing device senses IR light bydetecting variation in a secondary attribute that responds to the heatabsorbed when the IR light is applied thereon. One of the secondaryattribute that is sensed is the TCR (Temperature Coefficient ofResistance). In conventional resistive-type sensing devices which takeadvantage of the TCR of the material, a resistive-type sensing part ismade of Vanadium Oxide (VOx), poly-silicon, armorphous-silicon,thermistor ((MnNiCO)₃O₄), etc. These materials have an advantage thatthe TCR (ratio of resistance variation to temperature variation) ishigh, however they have a disadvantage that performance seriouslydeteriorates at low frequencies due to excessive flicker noise (that is,1/f noise) caused by their inherent characteristics.

Also, such a conventional IR sensing device sometimes includes a chopperfor resetting a sensing part by periodically blocking heat in the formof the thermal image that is incident on the array. However, the chopperlimits the operation of the IR sensing device, and makes theconstruction of the IR camera system more complicated and increasesmanufacturing costs.

Conventional IR sensing devices have an inherent design conflict betweensensitivity and image lag. To increase the sensitivity of the deviceeach pixel must be as thermally isolated from it's environment as muchas possible. A pixel that is very isolated from its environment is bydesign very slow to respond to changes in the scene and thus inducesimage lag. This new sensor has pixels that have thermal reset, thusallowing for the decoupling of sensitivity to the thermal time constantrequirements of video frame rates. The thermal resetting action of thisnew device eliminates image lag and allows for an additional increase insensitivity due to the elimination of the so called “TemperatureFluctuation Noise” component in the noise equations.

The present applicant has proposed a semiconductor device in whichcrystalline silicon thin film formed by a SOI (Silicon On Insulator)substrate manufacturing method is used as a sensing part, and a sensingstructure part having a serpentine shape discharges heat by touching asubstrate spaced apart downward from the sensing structure part, whichhas been registered as Korean Patent No. 704,378.

The semiconductor device is an improvement on conventional technologiesin view of sensitivity, simplicity of structure and manufacture andelimination of image artifacts like image lag.

SUMMARY

The present invention improves the performance of sensing infrared (IR)light and images.

Also, the present invention provides a micro-bolometer type IR sensingdevice having a structure for optimizing the electrical, mechanical,thermal and sensing characteristics of a serpentine structure.

According to an aspect of the invention, there is provided asemiconductor device in which a sensing structure part formed as a beamstructure discharges heat absorbed therein by being elastically deformedand thus touching a heat discharge part which is separate from thesensing structure part. In the sensing structure part, a light-absorbingpart is formed into one unit with the sensing part, with thelight-absorbing part balanced in equal part above and below the upperand lower surfaces of the sensing part, as seen in section view.

The sensing part may be made of a material with variation in thesecondary attribute according to the heat absorption of thelight-absorbing part, for example, a material with variation in TCR orin ferroelectricity according to the heat absorption of thelight-absorbing part.

According to another aspect of the invention, the light-absorbing partis formed at the left and right sides of the sensing part, as well as atthe upper and lower sides of the sensing part, thereby surrounding allof the sensing part.

According to another aspect of the invention, the sensing structure parthas a meander structure which is meandered while advancing and returningand shows a shape ‘⊂’ or a shape ‘⊃’ in turns at curved portions, asseen from above, near at least one end where the sensing structure partis supported. This meander increases the apparent stiffness of the wholestructure without having to increase the size of the structure, andincrease in the size of the structure would increase heat flow away fromthe sensor, which is not desirable.

According to another aspect of the invention, the light-absorbing partis made of Silicon nitride Si₃N₄, and the sensing part is made of a thinfilm of crystalline.

According to an embodiment of the present invention, there is provided asemiconductor device manufacturing method including: applying a sensinglayer on a handle wafer; patterning the sensing layer to form a cavity;forming a sensing part pattern having a beam structure in the cavity;applying a light-absorbing layer on the sensing part pattern; turningthe entire structure over and removing the handle wafer; and applying anadditional light-absorbing layer on the rear surface of thelight-absorbing layer.

According to another aspect of the present invention, the cavity isfilled with a filling layer during the process, and the filling layer isremoved in the final step of the process.

According to another aspect of the present invention, another absorbedheat discharge layer is applied on the filling layer. In order to makethe lower surface of the absorbed heat discharge part flat to improveefficiency in heat dissipation, the upper surface of the filling layeris polished in advance to be flat.

According to the present invention, since the light-absorption part isformed on the upper and lower surfaces of the sensing part, or allaround the sensing part, absorption of infrared energy can be improved,the creation of undesired curvature in the sensing structure part can beavoided, and accordingly the durability of the resultant sensor can beimproved, compared to the case of having a single sided light-absorbingpart.

Also, in the sensing structure part, since the sensing part is made of athin film of crystalline silicon, and the light-absorbing partsurrounding the sensing part is made of silicon nitride Si₃N₄, there isno interdependency between the mechanical and thermal characteristics ofthe sensing structure part so that the mechanical and thermalcharacteristics can be controlled independently, resulting in theimprovement of both sensitivity and operation speed.

Furthermore, since the present invention resets absorbed heat using anelastic deformation structure based on MEMS technologies; high thermalreset speed is achieved, which provides advantages for videoapplications by the elimination of image-lag.

Also, since a reset structure for discharging absorbed heat is providedon a substrate below the sensing structure part, the light-absorbingarea needs not to be sacrificed. Also, since such elastic deformation isdriven by electrostatic deformation when a potential difference isapplied, driving circuits for the electrostatic deformation can beformed by a CMOS process, and accordingly the entire semiconductordevice can be manufactured only by CMOS processes. Furthermore, thelight-absorbing area needs not to be sacrificed since CMOS circuits areformed below the sensor structure.

Also, in the semiconductor device manufacturing method according to thepresent invention, by forming a cavity in the sensing layer, andprocessing the sensing layer to form a sensing part, the thickness ofthe sensing part is thin so that mechanical stiffness is low, therebyfacilitating mechanical deformation and improving responsecharacteristics upon discharging absorbed heat. A thin cross sectionalso is advantageous to prevent parasitic heat leakage from the sensorthrough the support beams and thus increases sensitivity.

Also, according to the semiconductor device manufacturing method, sincea filling layer fixes the sensing part pattern in the cavity duringprocessing, no mechanical stress remains in the resultant sensorpattern. Accordingly, the sensor characteristics are ensured andresponse characteristics are further improved.

Additional aspects of the invention will be set forth in the descriptionwhich follows, and in part will be apparent from the description, or maybe learned by practice of the invention.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of theinvention, and together with the description serve to explain theaspects of the invention.

FIG. 1 is a plan view of the pixel in the semiconductor device accordingto an embodiment;

FIG. 2 is a cross-sectional view of the semiconductor device illustratedin FIG. 1;

FIG. 3 shows a status where a sensing structure part is elasticallydeformed to discharge heat there from, in the semiconductor deviceillustrated in FIG. 2; and

FIGS. 4A through 4J are a view for explaining a semiconductor devicemanufacturing method according to an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

The invention is described more fully hereinafter with reference to theaccompanying drawings, in which exemplary embodiments of the inventionare shown. This invention may, however, be embodied in many differentforms and should not be construed as limited to the exemplaryembodiments set forth herein. Rather, these exemplary embodiments areprovided so that this disclosure is thorough, and will fully convey thescope of the invention to those skilled in the art. In the drawings, thesize and relative sizes of layers and regions may be exaggerated forclarity. Like reference numerals in the drawings denote like elements.

It will be understood that when an element or layer is referred to asbeing “on” or “connected to” another element or layer, it can bedirectly on or directly connected to the other element or layer, orintervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on” or “directly connected to”another element or layer, there are no intervening elements or layerspresent.

FIG. 1 is a plan view of a semiconductor device according to anembodiment, and FIG. 2 is a cross-sectional view of the semiconductordevice. Referring to FIGS. 1 and 2, the semiconductor device includes anabsorbed heat discharging part 3, and a sensing structure part 1 formedas a beam structure spaced apart from the absorbed heat discharging part3 and supported at both ends on the absorbed heat discharging part 3.

As illustrated in FIGS. 1 and 2, the sensing structure part 1 issupported at both ends on the absorbed heat discharging part 3, but maybe supported at its at least one end on the absorbed heat dischargingpart 3. For example, the sensing structure part 11 could have a spiralshape supported at one end on the absorbed heat discharging part 3. Inthis case, sensing parts extend in pairs along the spiral shape, andmeet at the end of the spiral shape to thus form a circuit.

The sensing structure part 1 includes a sensing part 13 with variationin electrical resistance according to heat, and light-absorbing parts 11and 15 formed as one unit with the sensing part 13 and converting theenergy of incident photons into heat. However, the sensing part 13 maybe made of an arbitrary material with variation in the secondaryattribute, such as its physical, chemical properties, according to heat,the variation in the secondary attribute capable of being measured.

The light-absorbing parts 11 and 15 surround the sensing part 13 andtogether form the beam structure. However, the present invention is notlimited to this structure, and the light-absorbing parts 11 and 15 maybe formed only above and below the sensing part 13 According to thecurrent embodiment, although the light-absorbing parts 11 and 15 and thesensing part 13, are made of materials of different thermal expansioncoefficients but are formed as one unit, stress due to thermal expansionis cancelled, thus avoiding the creation of undesired curvature, sincethe light-absorbing parts 11 and 15 are symmetrical to the sensing part13. The manufacturing processes of the semiconductor device have to bebalanced in order to avoid the accumulation of deformation due to thestress of the light-absorbing parts 11 and 15, which will be describedlater.

Also, an additional thickness obtained by forming two layers of thelight-absorbing parts 11 and 15, instead of forming the light-absorbingparts 11 and 15 as a single layer, improves absorption of infrared (IR)energy. Increasing the thickness by forming two layers is more effectivethan doubling the thickness of a single layer. The reason is because thethermal time constant in a vertical direction is reduced and thus heattransfer in the vertical direction is increased.

Since a fully-passivated structure where the light-absorbing parts 11and 15 fully surround the sensing part 13 is provided, the life cycle ofthe sensing part 13 is increased, and the light-absorbing parts 11 and15 can be tuned to absorb photons of particular wavelengths by thesubstitution of material in parts 11 and 15 or more preferably bycoating parts 11 and 15 with and additional absorbing layer. Forexample, an application for detection of X-ray is expected.

The sensing structure part 1, as illustrated in FIG. 3, is elasticallydeformed and touches the absorbed heat discharging part 3, thusdischarging heat absorbed in the light-absorbing parts 11 and 15.According to an aspect of the present invention, the supported one endof the sensing structure part 1 has a meander structure which ismeandered while advancing and returning and shows a ‘⊂’ shape or a ‘⊃’shape in turns at curved portions, as seen from above. The meanderstructure contributes to greatly increase stiffness by constraining theangular components of deformation.

According to the current embodiment, the sensing structure part 1 isbased on a serpentine structure (that is, 91 and 95 in FIG. 1) which isnarrow in width and curved in form. The center portion 93 of the sensingstructure part 1 is formed as a grid pattern. The grid pattern is alsoeffective in increasing resistance because of having a narrow width toreduce the cross-section of the sensing part 13.

In the current embodiment, the sensing part 13 is made of Silicon OnInsulator (SOI), and the light-absorbing parts 11 and 15 surrounding thesensing part 13 are made of silicon nitride Si₃N₄. Due to the structurewhere the light-absorbing parts 11 and 15 made of silicon nitride Si₃N₄surround the sensing part 13, the mechanical and thermal characteristicsof the sensing part 13 can be optimized. That is, it is preferable thatthe beam structure has high stiffness and low thermal conductivity.However, conventionally, it was contradictory that the thickness of thebeam has to be increased to enhance stiffness, while the thickness ofthe beam has to be decreased to reduce thermal conductivity.

The stiffness of the sensing structure part 1 depends on thelight-absorbing parts 11 and 15 made of silicon nitride Si₃N₄, and itsthermal characteristics depend on the sensing part 13 made ofcrystalline silicon. Meanwhile, the electrical characteristics of thesensing structure part 1 can be controlled by adjusting an implantapplied to the sensing part 13 in the areas of 91,93 and 95, eachimplant can be independent from the others if necessary to tune theelectrical characteristics. Accordingly, by achieving desired stiffnessthrough the structure where the light-absorbing parts 11 and 15 surroundthe sensing part 13, improving thermal characteristics through thethinness of the sensing part 13, and optimizing electricalcharacteristics through adjustment of the implant applied to the sensingpart 13, an optimized sensor can be manufactured.

In the current embodiment, in order to effectively discharge heatabsorbed in the light-absorbing parts 11 and 15, a sufficient flatnessof the upper surface of the absorbed heat discharging part 3 which thesensing structure part 1 contacts upon deformation has to be ensured. Bymaking the upper surface of the absorbed heat discharging part 1 to besufficiently flat, an amount of heat dissipation through the contactupon deformation is much greater than an amount of heat dissipationthrough the structure where the sensing structure part 1 is supported onthe absorbed heat discharging part 3.

In the current embodiment, the absorbed heat discharging part 3 is ahandle wafer, but may have a multi-layer structure or an arbitrarystructure having a wide surface area and high thermal conductivity.

Electrodes 5 are provided to supply or receive electrical signals to orfrom the sensing part 13. Also, a heat discharge driving part, which isnot shown in the drawings, is provided to apply a potential differencebetween the sensing part 13 and absorbed heat discharging part 3, thuselastically deforming the sensing structure part 1 and resetting heatabsorbed in the absorbed heat discharging part 3. That is, the sensingstructure part 1 contacts the absorbed heat discharge part 3 throughdeformation by electrostatic actuation, thus discharging heatvertically. Of note in this system is the disparity between thermalleakage current between the two states of operation. In the non-resetstate the heat has to flow the long and winding serpentine structure andthus effectively isolates the sensing part 93 from any heat leakage thatcan interfere with high sensitivity. However, once the sensor isactuated against the heat discharging part 3, the heat flows verticallyout of the structure. In this configuration it is easy to obtain atleast 5 orders of magnitude difference in thermal conduction between thetwo states.

The resistance of the sensing part 13 can be detected by using a currentflowing through the sensing part 13. A signal proportional to thecurrent is stored in the pixel, and read and output through a readcircuit similar to that of a CMOS image sensor.

The driving circuits and sensing circuits described above are CMOScircuits, and are integrated together with the sensing structures in thesemiconductor device. The CMOS circuits can be integrated on the sidesof the sensing structure part 1, or on the rear portion of the handlewafer (that is, the absorbed heat discharge part 3). If the CMOScircuits are integrated on the rear portion of the handle wafer, thelight-absorbing parts 11 and 15 need not to be sacrificed and the areaused for receiving light can be optimized.

FIGS. 4A through 4J are a view for explaining a semiconductor devicemanufacturing method according to an embodiment. According to thecurrent embodiment, the semiconductor device manufacturing methodincludes: applying a sensing layer with variable resistance according toheat, on a handle wafer; forming a cavity by patterning the sensinglayer; forming a sensing part pattern having a beam structure in thecavity; applying a light-absorbing layer for converting energy ofincident photons into heat, along the sensing part pattern; turning theentire structure over and removing the handle wafer, thus exposing therear surface of the sensing part pattern; and forming an additionallight-absorbing layer on the rear surface of the light-absorbing layerapplied on the sensing part pattern, thereby forming a sensing structurepart having a beam structure.

Referring to FIG. 4A, first, an oxide layer 102 is applied on a handlewafer 101, a Si sensing layer 103 which is a silicon thin film is formedon the oxide layer 102, and then another oxide layer 104 is applied onthe Si sensing layer 103.

In the current embodiment, the sensing layer 103 with variableresistance according to heat is a SOI wafer which is manufactured usingan SOI substrate manufacturing process. Any suitable process for SOI canbe used.

Crystalline silicon has Temperature Coefficient of Resistance (TCR) of0.2%/° K. The TCR value is smaller than the TCR values (2-3%/° K.) ofVanadium Oxide (VOx), poly-silicon, armorphous-silicon, thermistor((MnNiCO)₃O₄), etc. However, in the case of crystalline silicon, noisegeneration is much less than in polysilicon, armorphous-silicon, etc. Incrystalline silicon, Johnson noise (or thermal noise) expressed byEquation 1 is the main noise contribution, but in polysilcon,armorphous-silicon, etc., flicker noise (or 1/f noise) is the main noisecontribution.V _(n)=√{square root over (4KTBR)}  (1)where V_(n) represents Johnson noise, K represents the Boltzmannconstant, B represents a frequency band, and R represents resistance.

Also, since the sensing layer 103 is made of crystalline silicon, itselectrical resistance increases and accordingly Signal Noise Ratio (SNR)is increased, so that sensor performance can be greatly improved. Thereason of increasing resistance is first to reduce current flowingthrough the sensing part 13. This is aimed to reduce the self-heatingfrom the bias current. Second, the reason is to improve SNR as seen inEquation 2.

$\begin{matrix}{{{S\; N\; R} = \frac{\left( {{i \cdot \left( {T\; C\; R} \right) \cdot \Delta}\;{T \cdot \sqrt{R}}} \right)}{\sqrt{4\; K\; T\; B}}},} & (2)\end{matrix}$where SNR represents signal noise ratio, i represents current, TCRrepresents temperature coefficient of resistance, ΔT represents a changein temperature, R represents resistance of sensor, K represents theBoltzmann constant, T represents the temperature, and B represents afrequency band.

Thereafter, as illustrated in FIG. 4B, a part of the silicon oxide film104 and the sensing layer 103 made of crystalline silicon is etched byreactive ion etching (RIE), so that a cavity 130 is formed. The cavity130 provides a space that is to be filled with polysilicon, and alsoreduces the thickness of the crystalline silicon layer which is thesensing part of the sensor region. In the transistor process, a thicksilicon layer is needed, but the sensing part 103 is formed thin becauseof having to be flexibly bent mechanically. This structure facilitatesmechanical deformation when heat is discharged from the final sensingstructure part, thereby improving the responsiveness of the sensor.

Thereafter, by performing ion implantation and annealing on the sensinglayer 103 exposed by etching, electrical resistance is adjusted.Accordingly, the electrical characteristics of the sensor are adjusted.

Then, as illustrated in FIG. 4C, the sensor part 103 and sacrificialoxide film 104 are subjected to RIE processing, so that a sensing partpattern is formed as a beam structure. In the specification, the term“beam structure” means a structure formed by weaving or linking beams toreduce the section area of the sensing part 13. The beam structure maybe a grid pattern of beams, a serpentine structure, a S-shapedstructure, a spring-shaped structure, etc. For the improvement ofmechanical characteristics, the supported one end of the sensingstructure part 1 can may be a meander structure which is meandered whileadvancing and returning and shows a ‘⊂’ shape and a ‘⊃’ shape in turnsat the curved portions, when seen from above. The meander structureimproves mechanical stiffness by minimizing angular deflection in thecurved portions. Also, by making the widths of the beams at the curvedportions wider than in the remaining parts, the mechanicalcharacteristics can be further improved.

Thereafter, a SiO₂ pad oxide layer 105 is grown. The SiO₂ pad oxidelayer 105 acts to electrically isolate the sensing part 13 from thelight-absorbing parts 11 and 15 in the sensing structure part 1 (seeFIG. 2).

Then, referring to FIG. 4D, light-absorbing parts 106 and 106-1 made ofsilicon nitride are deposited on the pad oxide layer 105. Here, thelight-absorbing part 106 is self-aligned by the cavity. The referencenumber 106 represents a light-absorbing part in the sensor region, thereference number 106-1 represents a light-absorbing part formed outsidethe sensor region. The light-absorbing layer 106 or 106-1 for convertingenergy of incident photons into heat may be a single layer or amulti-layer structure made of any one of materials, such as SiO₂ andSi₃N₄, suitable for the CMOS process.

Then, as illustrated in FIG. 4E, the cavity is all filled withpolysilicon 107. Then, the surface of the wafer is polished to be flatby chemical-mechanical polishing (CMP) until the silicon nitride outsidethe sensor region is exposed. Here, the silicon nitride acts as a CMPetch stop. Thus, the polysilicon 107 is at the nearly same height as thesilicon nitride, and the upper surface of the polysilicon 107 isprocessed to a flat surface having a thickness of about 200 nm. It isimportant that the lower surface of an oxide layer 108, that is, theinterfacial surface between the polysilicon 107 and oxide layer 108 isflat. This is because the flat interfacial surface widens the contactareas between the sensing structure part 1 and the absorbed heatdischarging part 3, thus increasing the amount of heat dissipation (seeFIGS. 2 and 3).

Then, the silicon nitride 106-1 is stripped off, and an oxide layer 108that is to be part of the absorbed heat discharge layer 3 is appliedthereon, the surface of the oxide layer 108 is polished to provide abonding surface.

Next, another handle wafer 111 (see FIG. 4F) is bonded to the bondingsurface. Thereafter, the original SOI wafer handle, that is, the handlewafer 101 is removed by back-grinding and thus the rear portion of thesensing structure part 1 is exposed. Then, as illustrated in FIG. 4F,the entire structure is turned over, so that a new SOI wafer in whichthe sensing structure part 1 is buried is provided.

Successively, the wafer is patterned by lithography until the patternsof the sensor region are all exposed. During the lithography, the sensorpatterns are firmly supported by the polysilicon 107 filled in thecavity 130, and another cavity is formed. The cavity also acts to reducethe thickness of the sensor and provides a space in which polysiliconwill be filled. Then, a sacrificial oxide layer is deposited on theupper surface of the sensor region, and the oxide layer of the remainingportion except for the sensor region is removed by RIE using a mask.Accordingly, a pad oxide layer 112 for isolation between thelight-absorbing part 113 and the sensing part is additionally grown.

Referring to FIG. 4G, a silicon nitride forming a light-absorbing part113 is additionally applied on the oxide layer. Accordingly, crystallinesilicon acting as a sensing part is all surrounded by thelight-absorbing part 113. Then, the oxide layer remaining on theoriginal polysilicon is removed and new polysilicon 107-1 is attached tothe previously filled polysilicon 107.

Referring to FIG. 4H, the polysilicon 107-1 is filled in the cavity nearthe sensing structure part 1 and thus merged with the previously filledpolysilicon 107. Then, CMP is performed so that the polysilicon 107 and107-1 is disposed at the same height as the light-absorbing part made ofsilicon nitride. Then, the silicon nitride is stripped off, and CMP andsurface polishing are additionally performed to achieve a flatnesssatisfying the requirements of the standard CMP process.

Then, a sacrificial oxide film 114 is grown. Thereafter, a silicon layer115 is deposited thereon, and the standard CMOS process is performed inthe structure illustrated in FIG. 4I, so that driving circuits areformed. Here, the CMOS processes for forming the driving circuits areperformed on the remaining regions except for the sensor region of thewafer. If the circuit-forming processes are terminated after a metalprocess, the sensor region is exposed using a pad mask. RIE is stoppedat the polysilicon. Then, in order to remove all polysilicon 107 and107-1 around the sensor region, anisotropic wet etching is performedusing Tetramethylammonium hydroxide (TMAH). The TMAH etching is 100:1selective to silicon over silicon nitride and oxide. Accordingly, asillustrated in FIG. 4J, the whole sensor structure part is exposed in amanner to float over the cavity, so that a MEMS device which operates asa sensor and is thermally reset is manufactured.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A method of manufacturing a semiconductor device, comprising: applying a sensing layer with variation in a secondary attribute according to heat, on a handle wafer; patterning the sensing layer, thus forming a cavity; forming a sensing part pattern having a beam structure in the cavity; forming a light-absorbing layer for converting energy of incident photons into heat, along the sensing part pattern; turning the entire structure over, removing the handle wafer, and thus exposing a rear portion of the sensing part pattern; and forming an additional light-absorbing layer on a rear portion of the light-absorbing layer formed on the sensing part pattern, thereby forming a sensing structure part having a beam structure.
 2. The method of claim 1, further comprising: after the forming of the light-absorbing layer for converting the energy of the incident photons into the heat, forming on the light-absorbing layer a filling layer to fill up the cavity, and after the forming of the additional light-absorbing layer, selectively removing the filling layer and exposing the sensing structure part in a manner to float it over the cavity.
 3. The method of claim 2, further comprising after the forming of the filling layer, forming an absorbed heat discharge layer on the filling layer.
 4. The method of claim 3, further comprising between the forming of the filling layer and the forming of the absorbed heat discharge layer, polishing the upper surface of the filling layer to make the upper surface of the filling layer flat.
 5. The method of claim 3, further comprising after the forming of the absorbed heat discharge layer, bonding another handle wafer on the upper surface of the absorbed heat discharge layer.
 6. The method of claim 1, wherein the applying of the sensing layer comprises applying a crystalline silicon thin layer by a layer transfer process.
 7. The method of claim 1, wherein the light-absorbing layer and the additional light-absorbing layer are made of silicon nitride Si₃N₄.
 8. The method of claim 2, wherein the filling layer is made of polysilicon, and the selectively removing of the filling layer is performed by anisotropic wet etching. 